1. Field of the Invention
The present invention relates to an anode having an anode active material layer on an anode current collector, a battery including the anode, and methods of manufacturing the anode and the battery.
2. Description of the Related Art
In recent years, portable electronic devices such as combination cameras (videotape recorder), mobile phones, and notebook personal computers have been widely used, and it is strongly demanded to reduce their size and weight and to achieve their long life. Accordingly, as a power source, a battery, in particular a light-weight secondary batter capable of providing a high energy density has been developed.
Specially, a secondary battery using insertion and extraction of lithium (Li) for charge and discharge reaction (so-called lithium ion secondary battery) is extremely prospective, since such a secondary battery is able to provide a higher energy density compared to a lead battery and a nickel cadmium battery. The lithium ion secondary battery has a cathode, an anode, and an electrolytic solution. The anode has an anode active material layer on an anode current collector.
As an anode active material contained in the anode active material layer, a carbon material such as graphite has been widely used. In recent years, as the high performance and the multi functions of the portable electronic devices are developed, further improvement of the battery capacity is demanded. Thus, it has been considered to use silicon, tin or the like instead of the carbon material. Since the theoretical capacity of silicon (4199 mAh/g) and the theoretical capacity of tin (994 mAh/g) are significantly higher than the theoretical capacity of graphite (372 mAh/g), it is prospected that the battery capacity is thereby highly improved.
However, in the lithium ion secondary battery, the anode active material inserting lithium in charge and discharge is highly activated, the electrolytic solution is easily decomposed, and lithium is easily inactivated. Thus, it is hard to obtain sufficient cycle characteristics. In addition, the secondary battery is easily swollen by being affected by gas generated in decomposition of the electrolytic solution. Thus, the swollenness characteristics may be lowered. The former disadvantage is significant in the case where silicon or the like having high theoretical capacity is used as an anode active material. The latter disadvantage is significant in the case where the battery structure is laminated film type using a film package member.
Therefore, to improve the various disadvantages of the lithium ion secondary battery, various considerations have been made. Specifically, to improve the load characteristics and the low temperature characteristics, a technique that a phenyl sulfone acid metal salt is contained in an electrolytic solution has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-056891). Further, to improve the battery characteristics, a technique that an organic alkali earth metal salt is contained in an electrolytic solution has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2000-268863). Further, to improve the storage characteristics and the cycle characteristics, a technique that a hydroxycarboxylic acid is contained in an electrolytic solution has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-092137). In addition, to prevent the battery capacity from being lowered, a technique that a carbon material as an anode active material is coated with a lithium alkoxide compound has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 08-138745).